1. Field of the Invention
The present invention relates to aircraft motor drive control apparatuses for driving motors mounted in aircrafts to drive devices installed in the aircrafts, and controlling the operational status of the motors.
2. Description of the Related Art
Various electrically powered devices are installed in an aircraft, and such devices are driven by motors (electric motors) mounted in the aircraft. One example of the aforementioned devices is an electrically powered hydraulic pump for supplying pressure oil to an actuator for driving a control surface formed as a moving surface (flight control surface) and configured as an aileron or an elevator, or the like, as disclosed in JP 2007-46790A. Another example is an electrically powered hydraulic pump for supplying pressure oil to an actuator that drives a moving surface configured as a flap, a spoiler, or the like, an electric actuator for driving a moving surface such as the above-mentioned control surface or spoiler, or a leg (a mechanism supporting the body of an aircraft on the ground) such as a landing gear (undercarriage).
A motor drive control apparatus (aircraft motor drive control apparatus) that is also mounted in the aircraft drives a motor for driving those devices, and controls the operational status of the motor. From the viewpoint of improvement in efficiency, it is possible to use, as such a motor drive control apparatus, a motor drive control apparatus including an inverter that has a switching element and drives a motor and a controller that performs a pulse width modulation control (PWM control) of this inverter.
In the above-described motor drive control apparatus including an inverter and a controller that performs PWM control, the control performance is improved by increasing the PWM frequency, which is the switching frequency (carrier frequency) of the switching element. However, an increase in the PWM frequency leads to an increase in a loss in the switching element that is proportional to the PWM frequency, resulting in an increase in the amount of heat generation as well. Therefore, it is desired to provide a motor drive control apparatus that can ensure control performance and suppress heat generation in a well-balanced manner.
On the other hand, JP 2010-57243A discloses, as a motor drive control apparatus provided in a vehicle, a motor drive control apparatus that controls the PWM frequency from the viewpoint of reducing the noise generated depending on the frequency band of the PWM frequency, in addition to the viewpoints of ensuring control performance and suppressing heat generation. Note that the motor drive control apparatus disclosed in JP 2010-57243A is configured to perform synchronous PWM control if the current supplied to the motor by an inverter or the torque generated in the motor is greater than a threshold. Furthermore, if the above-mentioned current or torque is smaller than the threshold, this motor drive control apparatus is configured to perform synchronous PWM control or asynchronous PWM control and set the PWM frequency higher than in the case where the above-mentioned current or torque is greater than the threshold.